Unraveling groundwater potential zones from alluvial plains using decision making method: A river scale analysis

• Morphometric attributes were computed of LRRB. • Multiscale SPI was applied to study drought/wetness scenario. • Integrated thematic layers-based analysis was applied to delineate GWPZ. • GWPZ map was prepared to categorize as excellent, good, fair and poor. • Validation of GWPZ by groundwater depth and soil moisture data. Due to climate change many basins are under water stress condition due to erratic rainfall. Hence, we aimed to study rainfall change over the last thirty-two years and to identify the new groundwater potential zones (GWPZ) using the remote sensing-based products, meteorological, hydrogeological, and groundwater level data in the lower Rapti river basin. The monthly data of thirty-two years (1990-2022) of eight stations viz. Balrampur, Shravasti, Siddharth Nagar, Maharajganj, Sant Kabir Nagar, Gorakhpur, Deoria, and Kushinagar were tested for standardized precipitation index (SPI) at multi-time scale (SPI-1, SPI-3, SPI-6, SPI-9, SPI-12, and SPI-24) to decipher wetness and dryness condition in the area. Afterwards, impact of rainfall was correlated with surface drainage characteristic and sub-surface recharge zone. Henceforth, different data sets pertaining to lithology, rainfall, geology, drainage density, geomorphology, land use/land cover, soil, slope and elevation. Relative importance of thematic layers, weights on Saaty’s scale was determined by analytical hierarchy process in order to normalize and standardize the weights. Eventually, in the GIS environment all thematic layers were combined using the weighted overlay method (WOM) for delineation of GWPZ. Result of GWPZ was validated with groundwater level and soil moisture data and categorized as excellent, good, fair and poor.